The production of high pressure decorative laminates has expanded in recent years to the extent that millions of square feet of product are now being produced annually. These laminates are used for furniture, cabinetry, vertical surfaces and the like. Ordinarily, the laminates are produced by heat and pressure consolidating at least one kraft paper core sheet which has been impregnated with a thermosetting phenol/formaldehyde resin and a decorative sheet that is impregnated with a melamine/formaldehyde resin which does not undergo any noticeable color deterioration upon subsequent lamination. The decorative sheet is usually dyed or pigmented to a selected color or it may have printed thereon a specific design, pattern etc. such as a geometric figure or a floral design. The printed matter may also constitute a wood grain print such that the finished laminate represents naturally occurring wood. Frequently, the decorative sheet has a fine quality paper impregnated with a color stable thermosetting resin as an overlay sheet thereupon which acts as a barrier to avert abrasion of the decorative sheet and thus preserve its printed character.
The trend in recent years has been toward extremely thin, light weight, low cost decorative laminates which are somewhat flexible, dimensionally stable and resistant to cracking and/or glue line failure. In accordance with the trend, U.S. Pat. Nos. 3,547,769 and 3,589,974 have recently set forth variations in the production of such laminates wherein overlay sheets are omitted and resin layers are substituted therefor, or different paper sheets, e.g., acrylic paper, have been employed. The properties of decorative laminates have also been varied by the incorporation of resins other than only melamine/formaldehyde or phenol/formaldehyde into the decorative and core sheets, see U.S. Pat. Nos. 3,218,225 and 3,220,916.
In the past, it was generally thought that tough laminates required the presence of a resin impregnant therein which was known to impart toughness to decorative laminates. Phenol/formaldehyde resins provided this property in the past and recently elastomer modified resinous systems such as acrylonitrile-butadiene copolymers, alone or with polyvinyl chloride etc. have been employed for this purpose, see above patents, also U.S. Pat. No. 3,798,117.
The above-mentioned copending patent application discloses and claims thin, tough and dimensionally stable laminates which contain no phenolic resin components and no elastomeric copolymers. The phenolic and/or elastomeric materials have been replaced by melamine/formaldehyde-acrylic polymer admixtures which are impregnated into the core sheet or sheets and the decorative sheet in varying amounts. As a result, thin, tough, dimensionally stable, decorative laminates which can be bonded to a self-supporting substrate such as plywood, particleboard, etc., and which are free of phenol/formaldehyde resins are produced. Additionally, the fact that phenol/formaldehyde resins are not employed enables water-based impregnants to be used in many instances, thereby eliminating the need for utilizing solvents which necessitate recovery due to anti-pollution requirements. The excellent dimensional stability of the laminates also enables them to be bonded to metal substrates without experiencing the laminate cracking and adhesive bond failure which usually accompanies laminates of this type.
One property of the laminates set forth in the above-identified patent application which is not as attractive as the consumer may desire is the abrasion resistance thereof. That is to say, when the laminates are employed as the horizontal surface of structures wherein excessive contact with abrading materials occurs, the wearing thereof tends to detract from the aesthetic appearance of the structure. As a result, if the abrasion resistance of the laminates could be increased, a long felt need would be satisfied.